International Joint Research Center of National Animal Immunology, College of Veterinary Medicine, Henan Agricultural University, Zhengdong New District Longzi Lake 15#, Zhengzhou, 450046, Henan, People's Republic of China.
Department of Life Science, Zhengzhou Normal University, Zhengzhou, 450044, Henan, People's Republic of China.
Arch Virol. 2023 May 13;168(6):161. doi: 10.1007/s00705-023-05791-w.
Porcine circovirus 4 (PCV4) is a recently discovered circovirus that was first reported in 2019 in several pigs in Hunan province of China and has also been identified in pigs infected with porcine epidemic diarrhea virus (PEDV). To further investigate the coinfection and genetic diversity of these two viruses, 65 clinical samples (including feces and intestinal tissues) were collected from diseased piglets on 19 large-scale pig farms in Henan province of China, and a duplex SYBR Green I-based quantitative real-time polymerase chain reaction (qPCR) assay was developed for detecting PEDV and PCV4 simultaneously. The results showed that the limit of detection was 55.2 copies/μL and 44.1 copies/μL for PEDV and PCV4, respectively. The detection rate for PEDV and PCV4 was 40% (26/65) and 38% (25/65), respectively, and the coinfection rate for the two viruses was 34% (22/65). Subsequently, the full-length spike (S) gene of eight PEDV strains and a portion of the genome containing the capsid (Cap) gene of three PCV4 strains were sequenced and analyzed. Phylogenetic analysis showed that all of the PEDV strains from the present study clustered in the G2a subgroup and were closely related to most of the PEDV reference strains from China from 2011 to 2021, but they differed genetically from a vaccine strain (CV777), a Korean strain (virulent DR1), and two Chinese strains (SD-M and LZC). It is noteworthy that two PEDV strains (HEXX-24 and HNXX-24XIA) were identified in one sample, and the HNXX-24XIA strain had a large deletion at amino acids 31-229 of the S protein. Moreover, a recombination event was observed in strain HEXX-24. Phylogenetic analysis based on the amino acid sequence of the PCV4 Cap protein revealed that PCV4 strains were divided into three genotypes: PCV4a1, PCV4a2, and PCV4b. Three strains in the present study belonged to PCV4a1, and they had a high degree of sequence similarity (>98% identity) to other PCV4 reference strains. This study not only provides technical support for field investigation of PEDV and PCV4 coinfection but also provides data for their prevention and control.
猪圆环病毒 4 型（PCV4）是一种新发现的圆环病毒，于 2019 年在中国湖南省的几头猪中首次报道，也在感染猪流行性腹泻病毒（PEDV）的猪中被鉴定出来。为了进一步研究这两种病毒的混合感染和遗传多样性，我们从河南省 19 个大型养猪场的患病仔猪中采集了 65 份临床样本（包括粪便和肠道组织），并开发了一种用于同时检测 PEDV 和 PCV4 的双重 SYBR Green I 实时荧光定量 PCR（qPCR）检测方法。结果表明，PEDV 和 PCV4 的检测限分别为 55.2 拷贝/μL 和 44.1 拷贝/μL。PEDV 和 PCV4 的检测率分别为 40%（26/65）和 38%（25/65），两种病毒的混合感染率为 34%（22/65）。随后，对 8 株 PEDV 分离株的全长 Spike（S）基因和 3 株 PCV4 分离株的部分基因组包含衣壳（Cap）基因进行了测序和分析。系统进化分析表明，本研究中的所有 PEDV 分离株均聚类在 G2a 亚群，与 2011 年至 2021 年来自中国的大多数 PEDV 参考株密切相关，但与疫苗株（CV777）、韩国株（强毒 DR1）和中国两株（SD-M 和 LZC）在遗传上有所不同。值得注意的是，在一个样本中鉴定出了两株 PEDV 分离株（HEXX-24 和 HNXX-24XIA），HNXX-24XIA 株的 S 蛋白第 31-229 位氨基酸有一个大的缺失。此外，在 HEXX-24 株中观察到重组事件。基于 PCV4 Cap 蛋白氨基酸序列的系统进化分析表明，PCV4 株分为三个基因型：PCV4a1、PCV4a2 和 PCV4b。本研究中的三株属于 PCV4a1，与其他 PCV4 参考株具有高度的序列相似性（>98%同一性）。本研究不仅为 PEDV 和 PCV4 混合感染的现场调查提供了技术支持，也为它们的防控提供了数据。
